Preparation and properties of nanocrystal SmBO_3 by nitrate-citrate sol-gel combustion method

Nanocrystal SmBO3 powders were synthesized by nitrate-citrate sol-gel combustion method. The phase evolution, morphologies and absorbency of the synthesized powders were characterized by X-ray diffraction （XRD）, Field emission scanning electronic microscope （FESEM）, Fourier transform infrared spectroscopy （FFIR） and UV-3101PC spectrophotometer （UVPC）, respectively. XRD and FESEM results showed that pure SmBO3 phase was obtained at 750 ℃, with an average original particle size of about 100 nm. FTIR showed that there were apparently concentrated absorbent peaks between 500 and 1400 cm^-1. Moreover, the reflectivity of the powders apparently decreased at the wavelength between 1.05 and 1.15 μm. Therefore, SmBO3 might be a kind of absorbent material for infrared laser.

Nano crystalline powders of NiCu ferrite and NiCuZn ferrite prepared from citrate gel method： Synthesis and cnaracterzation

Nano size nickel copper ferrite powders （NiCuFe204） and nickel copper zinc ferrite powders have been prepared by a citrate gel precursor method. The resulting powders were characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM）. The results showed that nickel copper ferrites and nickel copper zinc ferrites were also in the nanosaele. The NiCu ferrite powders showed extensive XRD fine broadening and sizes of crystals were calculated （from the XRD line broadening） as 26 run-44 run over the temperature range is 200-800℃. The NiCuZn ferrite powders showed XRD line broadening and sizes of of crystals were calculated 46-65 nm over 200-800℃.

Magnetic Properties of Ni-Zn Ferrites by Citrate Gel Method

Ni-Zn ferrite with a nominal composition of Ni1-xZnxFe2O4 (x = 0, 0.2, 0.6, 0.8, 0.9) are prepared by citrate gel method and characterized by X-ray diffraction. Magnetic properties of all samples are obtained by using VSM (Vibrating Sample Magnetometer) in the range of 10 Koe. The saturation magnetization values of the samples are carried out from the B-H loop. The effect of composition on saturation magnetization and magnetic moment are studied in this paper. The results showed that Saturation magnetization and magnetic moment values increases gradually as Zn2+ composition increases, it reaches maximum value 70.28 emu/gm for (x = 0.6) and decreases further with increasing Zn2+ composition.

Dielectric Properties of Ni-Zn Ferrites Synthesized by Citrate Gel Method

Ni-Zn ferrite with composition of Ni1-xZnxFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 0.9, 1.0) were prepared by citrate gel method. The Dielectric Properties for all the samples were investigated at room temperature as a function of frequency. The dielectric constant shows dispersion in the lower frequency region and remains almost constant at higher frequencies. The frequency dependence of dielectric loss tangent (tan δ) is found to be abnormal, giving a peak at certain frequency for mixed Ni-Zn ferrites. A qualitative explanation is given for the composition and frequency dependence of the dielectric loss tangent.

Synthesis of Spin-ladder Sr_(14)Cu_(24)O_(41)Material by Citrates Sol-gel Method

A new process to synthesize polycrystalline samples of Sr14Cu24O41 was presented. Firstly, dry gel powder of Sr14Cu24O41 was synthesized by the citrates sol-gel method, using Sr（NO3）2, Cu（NO3）2, ethylene glycol and citrate acid as raw materials. Then, polycrystalline samples of Sr14Cu24O41 were prepared by solid-state reaction. Thermal Gravimetric and Differential Thermal Analysis（TG-DTA） showed that the temperature for solid-state reaction is at 942 ℃. The samples are identified to be single phase by X-ray Diffraction（XRD） and Scanning Electron Microscopy（SEM）. The SEM pictures showed that the first-step particles were at even size of about 100 nm by this technique. The electronic transport measurements showed that the doping compound were semiconductor with a crossover temperature T in the Arrhenius plot of the resistivity versus temprature.

Characterization of Chromium Substituted Cobalt Nano Ferrites Synthesized by Citrate-Gel Auto Combustion Method

Co-Cr nano-ferrites, having the chemical formula CoCrxFe2-xO4 (where x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0), were synthesized by the Citrate-gel auto combustion method. Synthesized powders were sintered at 500°C for 4 hours in an air and were characterized by XRD, SEM and EDS. XRD analysis showed cubic spinel structure of the ferrites and the crystallite sizes (D) were found in the range of 6 - 12 nm. The values of lattice parameter (a) decreased and X-ray density (dx) increased with the increase of Cr content. Scanning Electron Microscopic (SEM) studies revealed nano crystalline nature of the samples. An elemental composition of the samples was studied by Energy Dispersive Spectroscopy (EDS). The observed results can be explained on the basis of composition and crystal size.

Nanosized Nickel Oxides Derived from the Citrate Gel Process and Performances for Electrochemical Capacitors

Nanosized nickel oxide powders were prepared by thermal decomposition of the nickel citrate gel precursors. The thermal decomposition and powder materials derived from calcination of these gel precursors with various ratios of citric acid （CA） to nickel at different temperatures and times were characterized by thermal analysis （TG/DTA）, scanning electron microscopy （SEM）, x-ray diffraction （XRD）, and measurement of specific surface area （BET） with porosity analyses. The optimized processing conditions of calcination temperature 400℃ for 1 hour with the CA/Ni ratio of 1.2, were determined to produce the nanosized nickel oxide pow- ders with a high specific surface area of 181 m^2/g, nanometer particle sizes of 15-25 nm, micro-pore diameter distribution between 4-10 nm. The capacitance characteristics of the nanosized nickel oxide electrode in various concentrations of KOH solutions were studied by the cyclic voltammetry （CV） exhibiting both a double-layer capacitance and a faradaic pseudocapacitance. The nanosized nickel oxide electrode shows a high cyclic stability and is promising for high performance electrochemical capacitors.

Citrate-Gel Synthesis and Luminescent Properties of α-Zn_3(PO_4)_2 Doped with Eu^(3+)

By using inorganic salts as raw materials and citric acid as complexing agent, α-Zn 3(PO 4) 2 and Eu 3+ doped α-Zn 3(PO 4) 2 phosphor powders were prepared by a citrate-gel process. X-ray diffraction (XRD), TG-DTA, FT-IR and luminescence excitation and emission spectra were used to characterize the resulting products. The results of XRD reveal that the powders begin to crystallize at 500 ℃ and pure α-Zn 3(PO 4) 2 phase is obtained at 800 ℃. And the results of XRD reveal that Eu 3+ exists as EuPO 4 in the powder. In the phosphor powders, the Eu 3+ shows its characteristic red-orange (592 nm, 5D 0- 7F 1) emission and has no quenching concentration.

微波辅助sol-gel法合成Bi_(0.5)Na_(0.5)TiO_(3)粉体及其压电性能研究

采用微波辅助溶胶-凝胶(sol-gel)法制备Bi_(0.5)Na_(0.5)TiO_(3)(BNT)粉体,通过DSC/TG,XRD,SEM,FT-IR等表征方法,分析BNT的反应历程,煅烧温度对BNT成分、晶粒尺寸和压电性能的影响.结果表明,当微波煅烧温度为650℃时,可合成出高纯度BNT粉体(30~120 nm),其居里温度为394℃,d_(33)=7.5 pC/N,ε_(r)=535.58,tanδ=0.29.对比传统马弗炉煅烧sol-gel法,微波辅助sol-gel法有利于提高BNT的介电性能和居里温度,降低介质损耗.

Nanosized Ni-Mn Oxides Prepared by the Citrate Gel Process and Performances for Electrochemical Capacitors

Nanosized Ni-Mn oxide powders have been successfully citrate gel precursors. The powder materials derived from prepared by thermal decomposition of the Ni-Mn calcination of the gel precursors with various molar ratios of nickel and manganese at different temperatures and time were characterized using thermal analysis （TG-DSC）, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and Brunauer-Emmet-Teller （BET）. The optimized processing conditions of calcination at 400℃ for 1 h with Ni/Mn molar ratio 6 were proved to produce the nanosized Ni-Mn oxide powders with a high specific surface area of 109.62 m^2/g and nanometer particle sizes of 15-30 nm. The capacitance characteristics of the nanosized Ni-Mn oxide electrode in various concentrations of KOH solutions were studied by the cyclic voltammetry （CV） and exhibited both a doublelayer capacitance and a Faradaic capacitance which could be attributed to the electrode consisting of Ni-Mn oxides and residual carbons from the organic gel thermal decomposition. A specific capacitance of 194.8 F/g was obtained for the electrode at the sweep rate of 10 mV/s in 4 mol/L KOH electrolyte and the capacitor showed quite high cyclic stability and is promising for advanced electrochemical capacitors.

Synthesis of Cu-Chromite Catalyzer by Citrate Sol-Gel

It has been introduced several ways for rising fuel burning rate. Using catalyzers is a common way to rising fuel burning rate. Cu-Chromite catalyzer used in solid fuels, as burning rate catalyzer in thermal decomposition of Ammonium Perchlorate and results were satisfying. This catalyzer is produced by several methods such as: ceramic, coprecipitating, sol-gel, vacuum depositioning, but this paper explains producing catalyzer by Citrate sol-gel. Thermal analysis is used for studying process also SEM, XRD, TEM, FTIR tests used for determination of particle sizes.

Preparation of Al_(2-x)Y_xW_3O_(12) powders by citrate sol-gel process

Al2-xYxW3O12 (x=0.2,0.5,0.8,1.0,1.2,1.5,1.7 and 2.0) powders were synthesized by citrate sol-gel process.The concentration of species in a citric solution for preparing Al2-xYxW3O12 powders was calculated.The powders were characterized by differential thermal analysis(DTA),thermogravimetry(TG),X-ray diffractometry(XRD) and scanning electron microscopy(SEM),respectively.No solid solution of Al2-xYxW3O12 is formed with x values varying from 0 to 2.0.The maximum solid solubility of Y2O3 in Al2W3O12 and Al2O3 in Y2W3O12 is less than 0.5.Y2W3O12 easily absorbs water in air and forms a composition of Y2W3O12·3.2H2O,and Al2W3O12 forms Al2W3O12·0.17H2O in the same condition.

TiO_(2)/CuO Films Obtained by Citrate Precursor Method for Photocatalytic Application

In the present work, the hybrid catalyst films of TiO2/CuO containing up to 10% in mol of copper were deposited onto glass surface. Precursor solutions were obtained by citrate precursor method. Films were porous and the average particle size was 20 nm determined by FEG-SEM analysis. The photocatalytic activities of these films were studied using Rhodamine B as a target compound in a fixed bed reactor developed in our laboratory and UV lamp. It was observed that the addition of copper to TiO2 increased significantly its photocatalytic activity during the oxidation of Rhodamine B. The degradation exceeded 90% within 48 hours of irradiation compared to 38% when pure TiO2 was used. Moreover, there was a reduction in the particles band gap energy when compared to that of pure TiO2. These results indicate that the TiO2/CuO films are promising catalysts for the development of fixed bed reactors to be used to treat effluents containing azo dyes.

Effects of Ni doping contents on photocatalytic activity of B-BiVO_4 synthesized through sol-gel and impregnation two-step method

To enhance the photocatalytic activity of B-BiVO4,Ni-doped B?BiVO4photocatalyst(Ni-B-BiVO4)was synthesized through sol-gel and impregnation method.The photocatalysts were characterized by XPS,XRD,SEM,EDS,BET and UV-Vis DRS techniques.The results showed that single or double doping did not change the crystalline structure and morphology,but the particle size decreased with Ni doping.The band gap energy absorption edge of Ni-B-BiVO4shifted to a longer wavelength compared with undoped,B or Ni single doped BiVO4.More V4+and surface hydroxyl oxygen were observed in BiVO4after Ni-B co-doping.When the optimal mass fraction of Ni is0.30%,the degradation rate of MO in50min is95%for0.3Ni-B-BiVO4sample which also can effectively degrade methyl blue(MB),acid orange(AOII)II and rhodamine B(RhB).The enhanced photocatalytic activity is attributed to the synergistic effects of B and Ni doping.

Synthesis and electrochemical properties of dual doped spinels LiNi_xAl_yMn_(2-x-y)O_4 via facile novel chelated sol–gel method as possible cathode material for lithium rechargeable batteries

LiMnOand LiNiAlyMnO（x= 0.50;y = 0.05-0.50） powders have been synthesized via facile solgel method using Behenic acid as active cheiating agent.The synthesized samples are subjected to physical characterizations such as thermo gravimetric analysis（TG/DTA）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,field-emission scanning electron microscopy（FESEM）,transmission electron microscopy（TEM） and electrochemical studies viz.,galvanostatic cycling properties,electrochemical impedance spectroscopy（EIS） and differential capacity curves（dQ/dE）.Finger print XRD patterns of LiMnOand LiNiAlMnOfortify the high degree of crystallinity with better phase purity.FESEM images of the undoped pristine spinel illustrate uniform spherical grains surface morphology with an average particle size of 0.5 μm while Ni doped particles depict the spherical grains growth（50nm） with ice-cube surface morphology.TEM images of the spinel LiMnOshows the uniform spherical morphology with particle size of（100 nm） while low level of Al-doping spinel（LiNio.5Alo.05Mn1.45O4） displaying cloudy particles with agglomerated particles of（50nm）.The LiMnOsamples calcined at 850℃ deliver the discharge capacity of 130 mAh/g in the first cycle corresponds to 94%coiumbic efficiency with capacity fade of 1.5 mAh/g/cycle over the investigated 10 cycles.Among all four dopant compositions investigated,LiNiAlMnOdelivers the maximum discharge capacity of 126 mAh/g during the first cycle and shows the stable cycling performance with low capacity fade of 1 mAh/g/cycle（capacity retention of 92%） over the investigated 10 cycles.Electrochemical impedance studies of spinel LiMnOand LiNiAlMnOdepict the high and low real polarization of 1562 and 1100 Ω.

Characterization and photoelectrochemical performance of Zn-doped TiO_2 films by sol-gel method

Zn-doped TiO2 (Zn?TiO2) thin films were prepared by the sol?gel method on titanium substrates with heat treatment at different temperatures. The effects of heat treatment temperatures and Zn doping on the structure, photocathodic protection and photoelectrochemical properties of TiO2 thin films were investigated. It is indicated that the photoelectrical performance of the Zn?TiO2 films is enhanced with the addition of Zn element compared with the pure-TiO2 film and the largest decline by 897 mV in the electrode potential is achieved under 300 °C heat treatment. SEM?EDS analyses show that Zn element is unevenly distributed in Zn?TiO2 films; XRD patterns reveal that the grain size of Zn?TiO2 is smaller than that of pure-TiO2; FTIR results indicate that Zn - O bond forms on Zn?TiO2 surface. Ultraviolet visible absorption spectra prove that Zn?TiO2 shifts to visible light region.Mott?Shottky curves show that the flat-band potential of Zn?TiO2 is more negative and charge carrier density is bigger than that ofpure-TiO2, implying that under the synergy of the width of the space-charge layer, carrier density and flat-band potential, Zn?TiO2 with 300 °C heat treatment displays the best photocathodic protection performance.

Tungsten nanoparticle-strengthened copper composite prepared by a sol–gel method and in-situ reaction

Tungsten nanoparticle-strengthened Cu composites were prepared from nanopowder synthesized by a sol–gel method and in-situ hydrogen reduction.The tungsten particles in the Cu matrix were well-dispersed with an average size of approximately 100–200 nm.The addition of nanosized W particles remarkably improves the mechanical properties,while the electrical conductivity did not substantially decrease.The Cu–W composite with 6 wt%W has the most comprehensive properties with an ultimate strength of 310 MPa,yield strength of 238 MPa,hardness of HV 108 and electrical conductivity of 90%IACS.The enhanced mechanical property and only a small loss of electrical conductivity demonstrate the potential of this new strategy to prepare W nanoparticle-strengthened Cu composites.

CHANGE OF CeVALENCE STATE DURING THE PREPARATION OF CeO_2 ULTRAFINE POWDER BY SOL－GEL METHOD

CeO2 ultrafine powder was prepared by sol-gel method.XRD showed that samples were amorphous when calcination temperature was below 230℃,and single phase CeO2 ultrafine powders could be obtained above 250℃.It was found that Ce(3+) and Ce(4+)coexisted in the dried gel,the content of Ce(3+)lowered gradually and that of Ce(4+)increased in samples when calcining temperature increased.Ce(3+)was converted to Ce(4+)completel at 250℃.

Encapsulation of Eu(TTA)_3 into MCM-41 Mesoporous Molecular Sieve by Sol Gel Method

The rare earth complex Eu(TTA) 3 was successfully encapsulated into MCM 41 mesoporous molecular sieve by the addition of the complex into the sol gel mixture for the synthesis of MCM 41 mesoporous material under microwave radiation. The as synthesized MCM 41 hosted Eu(TTA) 3 mesophase was confirmed to possess hexagonally ordered mesostructure and a uniform crystal size of about 30 nm with XRD and HRTEM techniques. Moreover, the IR spectrum, photoluminescence effect and fluorescence lifetime of the Eu(TTA) 3/MCM 41 hybrid were also studied. An increase in Stokes' shift and no change in luminescence lifetime were observed to the resultant mesophase in comparison with Eu(TTA) 3 in ethanol solution.

Nanostructured Yb:GGG polycrystalline powders via gel combustion method

Gadolinium gallium gamet （GGG） nanopowders doped with ytterbium ions （Yb：GGG） were synthesized with citric acid as a fuel via gel combustion method. The optimized conditions for preparing yb^3＋：Gd3Ga5O12 nanopowders were discussed. The heat behavior, structure and morphology of powders were analyzed with thermal analysis （TG-DTA）, X-ray diffraction （XRD）, infrared spectra OR） and transmission electron microscope （TEM）. TG-DTA analysis revealed that the weight loss of the precursor occured below 800 ℃ and its crystallization temperature was 830.6℃. XRD and IR analysis showed that the precursor converted directly into pure GGG at a relatively lower temperature （900 ℃） without any other intermediate phase. The lattice constant was 1.2377 calculated by extrapolation method. TEM results indicated that the spherical powders showed good dispersity and had a relatively narrow size distribution with average particle size of approximately 40-50 ran, which was favorable for good sinterability of Yb：GGG laser ceramic.